Undifferentiated B-cell lymphomas occur predominantly in children and young adults in a) a geographically delineated form, which is EBV associated, b) a sporadic, widespread form which is not EBV associated, and c) a form arising in certain immunodeficiency syndromes notably that occurring predominantly in homosexual drug abusers, which is also EBV associated. The goals of the present work are to gain information on the epidemiology, pathogenesis and biological differences among the several forms of undifferentiated lymphoma. Links have been established with a number of cancer centers in various parts of the world as part of a concerted effort to characterize, with more precision than has hitherto been achieved, differences in the spectrum of lymphoid neoplasia that occurs in different environments. The current emphasis is on molecular characterization of these tumors. In particular, we are comparing the molecular rearrangements in and EBV association of Burkitt's lymphoma from different regions. Biological studies are carried out on cell lines derived from all three of the above categories of undifferentiated lymphomas. Of particular interest is the expression of genes involved in specific chromosomal translocations associated with these tumors, namely the immunoglobulin genes and c-myc oncogene, and changes in the expression of these genes and other oncogenes during differentiation of the cell lines, and after inhibition of proliferation with antiimmunoglobulin antibodies. We are interested to determine whether the expresssion of the translocated c-myc gene is linked in Burkitt's lymphoma cells to the expression of immunoglobulin genes.